1. Technical Field
The present invention relates to an electronic apparatus which includes switching elements driven by controlling the voltage of control terminals, and an on-driving circuit which applies a constant current to the control terminal of the switching element to charge the control terminal of the switching element, thereby turning on the switching element.
2. Related Art
For example, a gate driving apparatus is disclosed in JP-A-2009-011049. The gate driving apparatus is an electronic apparatus which includes switching elements driven by controlling voltage of control terminals, and an on-driving circuit which applies a constant current to the control terminal of the switching element to charge the control terminal of the switching element, thereby turning on the switching element.
The gate driving apparatus drives an IGBT (insulated gate bipolar transistor). The IGBT is a switching element driven by controlling the voltage of the gate. The gate driving apparatus includes an on-constant current pulse gate driving circuit. The on-constant current pulse gate driving circuit is connected to a control source and a gate of the IGBT. The on-constant current pulse gate driving circuit is supplied with voltage from the control source, and applies a constant current to the gate of the IGBT to charge the gate of the IGBT, thereby turning on the IGBT.
If an IGBT having a large current capacity is required, a plurality of IGBTs having a small current capacity (hereinafter, referred to as “small current capacity IGBT”) may be connected in parallel. In particular, collectors of the plurality of small current capacity IGBTs are commonly connected, and emitters thereof are commonly connected. To drive the IGBT having a large current capacity configured by connecting the plurality of small current capacity IGBTs in parallel, by the gate driving apparatus, the on-constant current pulse gate driving circuit is connected to the gates of the plurality of small current capacity IGBTs.
Meanwhile, a capacitive component exists between the gate and the emitter of the small current capacity IGBT. In addition, an inductance component exists in lines connecting the plurality of small current capacity IGBTs in parallel. Hence, an LC resonance circuit is formed of a closed circuit in which a current flows through the gate and the emitter of one of the small current capacity IGBTs and into the emitter and the gate of the other of the small current capacity IGBTs. As a result, resonance occurs. Conventionally, to suppress this resonance, a resistor is connected between the on-constant current pulse gate driving circuit and the gate of the small current capacity IGBT. Hence, the amount of current flowing through the closed circuit can be suppressed. As a result, the resonance can be suppressed.
However, since the amount of current flowing through the closed circuit is suppressed to suppress the resonance, the value of resistance cannot be smaller. Hence, switching loss increases due to the resistance.